1. Field of Invention
This invention relates to a solar energy concentrator and, in particular, to a solar energy concentrator of the non-tracking type having temperature responsive means for controlling the flow of heat exchange fluid therethrough.
2. Brief Statement of the Prior Art:
A number of designs have been developed for solar energy concentrators with the objective of focusing or concentrating incident solar energy onto a flow channel of lesser surface area. Radiant energy concentrating devices such as optical lens, mirrored reflectors and the like have been suggested for this purpose. Concentration of the incident solar energy is desirable to obtain higher working temperatures of the heat exchange fluid than possible with flat plate collectors, thereby permitting more efficient power extraction. Most solar concentrators are of the tracking variety in which a flow channel for the heat exchange fluid is supported at the focus of a lens or reflector and the assembly is mechanically actuated to track the incident angle of sunlight which continually varies with the season of the year and time of day.
A solar concentrator of the non-tracking type is disclosed in U.S. Pat. No. 3,915,148. In this concentrator, a plurality of parallel flow channels are supported beneath a cylindrical Fresnel lens which concentrates the incident solar energy into a narrow beam of concentrated light energy and directs the beam to selected ones of the subjacent flow channels. The beam of concentrated light energy shifts between adjacent flow channels in response to the change in the incident angle of sunlight.
While the aforementioned patent suggests a construction of a solar energy concentrator which eliminates the complex mechanism necessary for tracking the continually varying incident angle of sunlight, it creates another unsolved problem. This latter problem is the design of suitable valve means that can be mounted in each of the flow channels to permit flow through only the flow channel which receives the beam of concentrated light energy. For efficient operation of the solar energy concentrator, it is essential that the valves employed in the flow channels tightly seal the flow channels which are not receptive to the beam of concentrated solar energy. It is also necessary that the valves respond quickly to temperature changes of the heat exchange fluid as the respective flow channel is exposed to the beam of concentrated light energy.